Highly basic bicyclic and tricyclic guanidine compounds have found applications in the field of organic synthesis and polymer additives. Unfortunately, current methods for synthesizing these compounds either produce noxious byproducts such as hydrogen sulfide or require very harsh conditions.
Bicyclic guanidines such as 1,5,7-triazabicyclo[5.5.0]dece-5-ene (TBD) have been prepared by using triamines in combination with reagents such as CS2 or dialkyl carbonates. The CS2 route is described in U.S. Pat. No. 4,797,487. This route has the benefit of using inexpensive starting materials and providing high yields. However, it also produces large amounts of the poisonous and malodorous compound hydrogen sulfide (H2S) as a reaction byproduct. The generation of H2S requires additional safety precautions as well as the use of expensive scrubbers to prevent its release into the environment.
A more recent approach is described in US Patent Publication 2009/0281314 and PCT publication WO2009/137728. The route disclosed therein uses cyclic urea as the one carbon source. This is an improvement over the CS2 route since no H2S is produced; however, the chemistry requires a multi-step process and harsh reaction conditions.
Accordingly, there remains a need for cost effective, inexpensive routes to polycyclic guanidines such as TBD.